How Much Force Did Josie and Charlotte Apply to the Sandbag?

[disque]

Homework Statement

Josie and Charlotte push a 12-kg bag of playground sand for a sandbox on a frictionless, horizontal, wet polyvinyl surface with a constant, horizontal force for a distance of 6 m, starting from rest. If the final speed of the sand bag is 0.5 m/s, what is the magnitude of the force with which they pushed

Homework Equations

F=MA
W=Fdelta(r)cos(theta)

The Attempt at a Solution

since cos0= 1 I thought it was 36 because W/6=F so w/6=12(.5) so how is W not 36. I'm obnviously forgetting a crucial step but don't understand where. Any help would be great, Thanks a lot.

 

[Delphi51]

Looks like you are using the idea that the work done equals the kinetic energy acquired.
That would be F*d = 1/2*m*v^2 and it should work well!

In writing F = 12(.5), you are confusing acceleration (unknown) with velocity (.5).

 

[disque]

Alright thanks a lot that makes sense! :)